[GRASS5] v.clean, v.in.ogr

[Radim Blazek]

I have moved cleaning functions from v.clean to the library
and added new functions for removing dangles and bridges (connecting
island and area).
v.in.ogr uses now some of these functions to clean polygons.
In addition v.in.ogr can now import more layers at the same time
and warnings are printed for degenerate polygons in input.

As a consequence, for example, import of TIGER is easier,
v.in.ogr dsn=input/2000/56015/ layer=CompleteChain,PIP output=t56015_all
v.type input=t56015_all output=t56015_all_bc type=line,boundary,point,centroid
v.clean input=t56015_all_bc output=t56015_all_ok tool=chdangle,chbridge thresh=-1
result is a vector map containing lines and boundaries linked to one table
and areas to another one.

Also few memory leakages were fixed in the library.

Radim